Treatment of aqueous liquids with halogens



I July 14, 1942. R. POMEROY 2,289,589

TREATMENT OF AQUEOUS. LIQUIDS WITH HALOGENS I Filed April 10, 1939 INVENTOR BY I W K O W ATTORNEYS Patented July 14, 1942 u-N TEfp STATES PATENT- osrlcs maximum or aqueous mourns wrm nsnoams Richard Pomeroy, Harbor City, cum, amignor to Wallace & Tiernan 00. 1110., aeuovme corporation or New York Kpplication April 10, 1939, Serial No. 287,005

9Chlms.

the materials from which sewers are commonly constructed, this corrosion commonly going so far that it results in causing the sewers to. collapse. In certain drinking water sulphides are found which are extremely objectionable to the consumer and my methodis adaptable to the elimination of such undesirable characteristics.

My invention is based upon my discovery that ii the electrode potential of the aqueous material being treated; is held within certain limits (which I have iound'to be readily determinable, as hereinaiter explained), diillculties from odors of hydrogen sulphide and corrosion caused therefrom will be eliminated. The treatment consists in the.

addition oi halogens, and I have'discoveredthat after treatment theelectrode potential will indi cate the eiIect of such added halogen in ranges below those detectible by ordinary methods 01 I chemical analysis:

- An example of my new method of treatment v comprises the addition of chlorine to the liquid undergoing treatment, the chlorine being added in sufllcient quantity to produce the desired result, notably substantial elimination of hydrogen sulphide (H28) and the conditioning of the liquid- -to such a state that hydrogen sulphide is not present, but in which the-chlorine is added in Y (Cl. 210-) This invention relates to the treatment of that its nuisance properties are eliminated at the lowest possible cost: (2) to treat water in such a manner as to eliminate undesirable substances such as sulphides and bring the water to a pre- 5 determined state 01 reconditioning at cost; and (3) to eliminate or prevent the formation oi gases or substances which are injurious to the materials from which sewers may be constructed. Among these gases may be mentioned hydrogen sulphide and sulphur dioxide.

For convenience of explanation I shall first.

describe the method as applied to the treatment of sewage, and by describing what I now consider to be a preferred term of apparatusior 1g practicing this method.

. Referring to the drawing, which illustrates the apparatus, a pipe II or other conduit is provided for handling. the ilow of sewase, 101' example in the direction indicated by the arrow-ii. For

m detection of its electrode potential, the sewage 'may be conveniently sampled, i'or instance by continuously withdrawing a small portion 01 it 'througha pipe ii. The addition of chlorine to the sewage may be advantageously eiiected at a point in the stream ahead of the sampling line j ll; for example, through the line "a from a suitably controllable source oi supply, not shown. Such source of supp y maycomprise a chlorinator or other i'eeding apparatus, as of types known;

so in the art. It will be understood that the sedie mentation basins, filters or like sewage treating equipment may be employed, it desiredin con lunction with the apparatus shown; indeed, for instance, the sampling of sewage through the pipe I! may bcwithdrajwn from a sedimentation basin through which the sewage is flowing, rather than from a simple conduit.

Although the electrode potential of the sewage may in some cases be detected in the. main stream quired to have chlorine present in such amounts that it could :be" detected by ordinary methodsoi much less quantity than would be required it 40 or sewage, a small sample ofthe main flow is.

i'ree chlorine were present after treatment and preterabl withdrawn through thepipe it" inaiso in much less qlantity than would be, re.-

cluding a valve II and thus passes into acontainer ll, the excess liquid being discharged through a pipe ll, The liquid discharged chemical analysis. The desired eiiect or result through the pipe," may be discarded or may be is" detected by the electrode potential oiflthe returnedtothepipell bytheuseot any welltreated liquid with respect'to a reference 'electrade, the potential .01 which is constant and independent 01' the trated liquid, and thediilerknown means. The pipe I2 is advantageously 01' such length as to introduce the sampled sewage into the bottom portion of the container, as

ence of potential so detected may be utilized for; shown, and if desired, a baiiie ll may be installed maintaining the desired effect by.- manually or .automatically controlling the addition of the, chlorine when and asneeded.

One of the most important new results accomplished by my method is themarked reduction 7 in the amount of chlorine required to produce the desired result in a variety oi'flelds oi applicationfi More generally stated, certain major oblasts-pt my invention may be summarized as iollows: (1) to treatsewagein such a manner in the container so that the sewage discharged in I extending into the liquid through tainer. In 'iormillustrated. this hali-cell'is so of the calomel type and includes a pipe -24 co g ride) the mer my and the chloride solution serving as necting the interior a the tube 2| with a reservoir 25 which may be open at its upper end, as shown. In such a calomel half-cell, the upper end of the reservoir 25, the pipe 24, and

the tube 2| may contain an electrolyte, usually a chloride solution such as a solution of potassium chloride. In such a half-cell, this electrolyte forms a salt bridge and should be in ionic communication with the liquid (e.-g., sewage) in the container I4. I! desired, the electrolyte may be in direct communication with this liquid through a gooseneck 21 at the, lower end of the tube 2|. In some instances, it is desirable to use a gelatinous plug 23 in this gooseneck'to prevent physical contact between the liquid in the container l4 and the electrolyte, but to permit the passage of ions therethrough, thus prevent- 7 ing excessive contamination or escape of the electhrough a stop-cock 30. This permits addition of the electrolyte or periodical renewal thereof.

The halt-cell also provides a wire 3! serving as an electrical conductor, this wire being shown sealed in the bottom wall the reservoir 25. A body of mercury 32 is in electrical contact with the wire 3|, and serves as the electrode oi the halt-cell 23. In the. reservoir 25 above the mercury 32, and saturated with the electro e, is a body 01 calomel (mercurous chlo- This body of calomel, together with an electrolyte, forms a combination of substances which may undergo chemical change with ionic fiow through the halt-cell. Thus, the chloride solution may react with the mercury 01! the electrode forming calomel, this chemical reaction beinga reversible one, depending upon the body 33, instead oi'being pure calomel, may com- .rection of fiow of the electrons. In practice; is I prise a mixture of mercury, calomel, andpotassium chloride.

An electrode 35 extends into the liquid in the container l4 and may be sealed in a tube 36 extending through the plug 23, as shown. This electrode may be of any suitable material, preterably one which does not materially react with the sewage or like'liquid in the container M.

I Electrodes oi. platinum or gold are very satisfactory though other materials can be utilized in tection is effected in a zone of electrode poten-' tial which is, according to my present discovery, substantially below any electrode potential which would be representative of a concentration of chlorine (i. e., a concentration measurable in-parts, or fraction of a, part, per million).

The potential difierence generated by this electro-chemical cell is determined, as aboveexprefer to apply the electrode potential developed by the cell in normally balanced opposition to a standard source of potential, whereupon any variation in the said potential of the cell results in a potential unbalance in the control circuit.

Means are provided in response to such unbalance for operating, for example, an indicating device, and also for adjusting the comparison source of potential so as to'restore balance.

Such a system is shown in the accompanying drawing as utilizing a battery 40 or other source of unidirectional potential shunted by a relatively high resistance 4| and connected by a conductor 42 to the electrode 35. The resistance 4| conveniently comprises a potentiometer, for example oi the slide wire type having an adjustable contact 43. It will now be understood that if the batter 40 is connected, as shown, so that it may always be susceptible of opposition to the potential developed by the cell, the contact 43 may be adjusted to a position of balance, i. e., a position wherein the voltage of the battery as proportioned by the potentiometer is equal and opposite to the voltage oil the cell.

Suitable means are provided for operating an indicating device in response to voltage unbalance between the cell and the potentiometer tentialand thus to balance the input circuit.

this regard. Preferably, the electrode 35 is spaced from thegooseneck- 21 and is either directly or indirectly laved by the incoming sewage.

The halt-cell 23 and the electrode 35 cooper- .ate in defining an electro-chemical cell that generates a potential difference which varies in magnitude with certain conditions in the sewage,

and which may be indicative, I have found, of

'a condltion'in the sewage where hydrogen sulphide (or for example, like odor-forming soluble sulphide) is absent. That is, when the electrode potential of the sewage, which may be detected as just described, reaches a definite and readily predeterminable zone, the result, I have now found, is a positive indication of the absence of the undesired sulphides; and the detection is tion of chlorine in the sewage-indeed, the denot, ior example, a detection of the concentra- Although other types of circuit, also preferably including amplifying means, may'be employed, the illustrated system includes two vacuum tubes 45 and 46, connected as follows. To a grid 41 of the former, and to a filament 48 of the latter, may\ be connected the adjustable contact 43, this being accomplished by a conductor 49. A grid 50 of the vacuum tube 46 and a filament 5| 0! the vacuum tubeili may be interconnected, as

shown, and connected to the mercury electrode 32 by a conductor 54. An intermittently-operated switch means 55 may be included in this conductor and may alsoinclude a suitably driven cam 51 periodically closing a switch 58.

Thus, when the electrode potential of the sewagedeparts from the value for which balance has existed in the input circuitie. g., a value in the desired zone, as herein explained), the grid of one tube will be positive, thus increasin theplate current of one of the tubes. At the same time the filament oi the other vacuum tube will be positively charged relative to the grid of that tube, thus tending to decrease the plate current in that tube. On the other hand, ii-the of the contacts 66 or 81.

electrode potential varies in the opposite direction from its previous value, these conditions will be reversed. It is thus clear that the plate currents of the tubes 45 and 46 can be used for control purposes, as to eflect balance restoring adjustment of the potentiometer and operation .01 a suitable indicating device .or the like. To

that end, I have shown a solenoid winding 59 in the plate circuit 01' the tube 45 and a solenoid winding 60 in the plate circuit of the tube 46.

Various means may be used for operatively connecting the solenoid windings with the'balance restoring and indicating apparatus. One

'to contfiil the amount of operation of the motor I 16 once the contact 65 engages either of the conmethod'oi' so doing includes the use oi a' relay I including an arm 6! p ivoted at 62 and carrying cores 63 and it which are respectively moved downward upon energization of the solenoid windings 59 and 60.- Small springs a may be' tacts 66 or 61; or 'an'auxiliary device may be used which allows the motor to operate for a predetermined length of time. It will be understood, however, that the shape of the cam '51. as

used, if desired, to assist in returning the arm 6| to neutral position. The arm 6i carries a contact 65 engageable with a contact 88 when the arm is moved in a clockwise direction, and

. engageablewith a contact 61 when the arm is moved in an anti-clockwise direction. Thus, when the plate currents are equal, the pull exerted by each solenoid winding-will be equal.

This will be the condition when there is' no change in the electrode potential of the sewage or like liquid. If, however, the electrode potential changes, more current will flow through one of the solenoid windings than the other, thus resulting in engagement between the contact 65 and one or the'other, as the case may be,

Any suitable means may be used for operating the potentiometer contact '43 to restore balance. For e ample, there is shown a motor 18, ar-

ranged through suitable mechanical connection -'diagrammatically indicated by the dotted line 14, to displace thecontact 43- in one direction or the other accordingly as the motor is caused to rotate one way or the other. In the embodi ment illustrated, a direct-current motor is 11- izedQthe armature being connected acro a source 11, a switch 18 being provided if desired. A double-wound field is used including windings l9 and 80, one end oi. each winding being interconnected and connected to one terminal of the source llby conductor 8|. The other terminal of the winding 19 is connected by a conductor 82- to the switch contact 66. Similarly, the other terminal of the winding 80 is connected by a conductor 83 to the switch contact 61. The arm Si is connected to the source I1 through a conductor 84 and through the switch 18.

Thus, when the arm 6| moves to bring the contacts 65 and 66 into engagement, current flows through one of the field windings while,

well as the speed of rotation thereof, will con-' trol this .i'actor ii an intermittent energization system is used. Further, any suitable means, not shown, may be used for controlling the frequency of operation of the switch 58. a In addition, suitable rheostats, potentiometers, etc., may

be used in the vacuum tube circuits to control the amplification thereof and to balance these tubes, if desired.

For conveniently carrying out the method of -my invention, suitable indicating means may be provided to indicate the electrode potential of the sewage as detected by the cell. One such means, as shown, may comprise a pointer 9| mechanically operated with orby the contact 43 (under. control of the motor 16) and adapted to move over a suitable scale, 90. In lieu of the pointer BI and scale 90, other suitable indicating means may be arranged for operationby the system illustrated, i. e., actuatedby rotation 'of the motor 16, and may include recording or indicating devices of well-known types.

It will now. be seen that the procedure may be conveniently as follows: As the sewage, for example, advances along the pipe l0, its electrode potential is detected by the described system, and variations of that potential are accurately registered on the indicator 90-9l. As will be ap- .preciated, particularly in the light of what is elsewhere said herein, the electrode potential range in which it is desired to maintain the -sewage-as positively representing a condition wherein objectionable sulphide,fior example, is absent (and being, in my method, an electrode ,potential zone definitely less and preferably when this arm moves to close thecontacts and G1, the other 01" the field windings is en;

a It will be understood that the field windings are so disposed that the armature oi the motor will be rotatedin one direction or the other according asone or the other of the windings is energized. It will thus be apparent that when the electrode potential detected b'y the cell decreases, the motor 16 will rotate in such direc tion as to decrease correspondingly the potential between the contact '43 and, conductor 42,

i. e., by adjustment of the contact upwards as seen in the drawing; and vice'versa, ii the electrode potential increases, the motor will adjust the contact arm in the opposite direction In either case, the contact arm 43 is thus ad much less than electrode potentials which would be obtained when thereis in the sewage a concentrationoi chlorine detectible' by such electrometric means)may be readily predetermined upon the scale 90. Accordingly, the operator or attendant observesthe indicato'r from time to time and adjusts the supply of chlorine (introduced through the pipe Ila) in order to keep the pointer is:- within the predetermined optimum range on the scale. Thus if the indicated electrode potential starts to decrease, the operator adjusts the feeding apparatus so as to increase .the 'quantity oi chlorine, and vice verse-whereby the amount of chlorine is economically maintained atQa necessary for its use to ,obtain the desired conditioner the sewage. In-

, deed, at certain timesin some installations, the I condition of the sewage may besuch as not to require the addition of any chlorine at an; under such circumstances, it will be readily appre- "ciated that the pointer 9| will stand in the pre-' determined optimum zone when the supply oi chlorinehas been completely shut oil. Ii subse- 1 trated or describedin detail.

. when used in practicing my present method, is

.and the control element of the chlorinator or other feeding device, whereby the latter. is automatically adjusted in accordance with variations of the electrode potential from the optimum zone. Devices suitable for such automatic control are available in various forms, as will now be appreciated by those familiar with the art, and such devices are therefore not here illus- For example, the motor I6 maybe arranged, through appropriate mechanical connection, to operate a control valve or othercontrolling instrumentality for varying so the rate of feed of a chlorinator or the like connectedto the line Ilia.

It will now be seen that theinvention afiords a highly economical procedure for the treatment of sewage, in that instead of adding relatively large quantities of chlorine to provide in the treated sewage free chlorine detectible by ordinary methods of chemical analysis (or detectible as' an electrode potential representative of chlorine contenti. e-., indicating concentration of chlorine), only so much chlorine need be added, if any, as to reach the optimum zone of electrode potential. Electrolytic cellapparatus suitable for detection of electrode potential, in carrying out my method as hereinabove described, i's also disclosed in my United States Patent #2,076,964, issued April 13, 1937, for Process and apparatus for water purification; although (as will now be understood) such cell,

utilized, and the associated apparatus is operated, in a difierent manner from that specificallydisclosed, in my said patent. It will be further understood that the structure of the cell and its various parts (including the half-cell and the structure and arrangement of the electrodes within the container l4) may be modified in various respectsfor example, as set forth .in my cited patent, particularly in the descriptive portion thereof beginning at line 60, second column,- page 3, and extending through line-2l,-first column, page 4.

Although my present method finds its chief application in the treatment of sewage, particularly in sewage disposal plants, the disclosed procedure may beapplied eficiently to other uses, such as hereinabove recited. Thus, for instance, the procedure may be applied to control the elimination of hydrogen sulphide content in water.

Although I have chiefly described my invention as relating to the elimination of hydrogen sulphide, it will be understood that the procedure is likewise applicable to the elimination of other objectionable sulphides, particularly odor-forming, soluble sulphides; indeed, the aqueous material under treatment may contain a plurality of sulphides (including hydrogen sulphide) and the desired results of sulphideelimination are readily attained simply by carrying out the described procedure. 70

It will be understood that throughout this ap plication and in the appended claims, I have employed the term halogen to mean not only elementary halogens but also those halogen compounds which are able to liberate either elemen- 75 (iiv tary halogen or hypohalous acids. These compounds include the hypohalous acids and their salts and N-halogen compounds, important members of which group are the chloramines. The described class or halogen compounds, 1. e., those able to liberate elementary halogen or hypohalous acids, will be readily understood by those familiar with the art.

By electrode potential as referred to herein is meant the potential as may be indicated by reading the voltage between an electrode immersed in the liquid being treated and the electrode of a standard calomel half-cell, the calomel half-cell being connected with the liquid being treated by means of a salt bridge or other means of ionic communication. It is recognized that this potential diflerence will not be the same with various types of electrodes used in the liquid being treated. Whilethe potentials as referred to herein were obtained by using a bright gold or platinum wire electrode in the liquid being treated and a standard saturated calomel half-cell, it is understood that corresponding readings of diflerent amounts would be obtained were other electrodes used, and such readings once obtained would .be of equal significance. It will be further understood that other half-cells may be employed (for example as explained in my Patent No. 2,076,964)

w as well as other electrodes; indeed in. any case,

it will be appreciated that if desired for purposes of calibration or initial setting, the detected potentials may be easily corrected in the usuai manner known to those skilled in the art, so as to obtain the efiective potential between an electrode and the so-called normal hydrogen half:

cell.

As heretofore explained, the method comprises the maintenance of the sewage, as by the addition of chlorine when necessary, within a pro-determinable optimum range of electrode potentials, corresponding to the point where hydrogen sulphide is eliminated. It will now be appreciated that this optimum range of electrode poten tials maybe readily predetermined for a given set of conditions or for a given installation wherein the method is to be practiced. For example, in using a cell of the type hereinabove spec ically described, (employing a noble metal electrode,

such as bright platinum or gold wire in contact with the sewage) and correcting the detected electrode potential of the cell to the equivalent of a cell employing the so-called normal hydrogen electrode-in accordance with the present standard practice of the art of electrometric determination-theoptimum range of electrode po tentials for elimination of sulphide difllculties as herein elsewhere explained, was found to fa l within a range between about l50 millivolts and about +400 millivolts-determinations of this character having been specifically made with sewage at Los Angeles County, California, as obtained in the sewage system of the Los Angeles,

-County Sanitation Districts.

' In general, the optimum zone for a given sewage will be found to lie within the limits Just stated, so far as most sewages or most localities are concerned; in the usual case, the actual optimum zone or range extends between considerably closer voltage values than the aforesaid limitsthe position of the actual optimum mne within those limits varying considerably with the locality of the @ewage. In any case, however, it will be understood, that the optimum range for liquid of any given general character, such as sewage in a given specific locality, may be readily determined by simple and rapid tests. In other words,

variations from the stated range of electrode potentials occasioned by differences in cell construction or by differences in the general charac- I to eliminate undesired offensive odor-producing characteristics thereof, which method comprises in combination, detecting the electrode potential of the treated material with respect to a stand ard reference potential and adding a halogen to the material when and as required to maintain the detected potential of the treated material below the-minimum potentialwhich would be detected if free chlorine were present in the material but above the maximum potential detected in the material when the undesired characteristic is present. I

2. The method of testing aqueous material to determine undesired offensive odor-producing characteristics thereof, which method comprises in combination, treating the material with a haloi en to reduce said characteristics, detecting the electrode potential of the material undergoing treatment with respect to a standard reference ino an indication when said electrode potential departs from a value below the minimum electrode potential which would be detected if free chlorine were present in the material"but above the maximum electrode potential detectable in the material when the undesired characteristic is present.

3. A method of treating sewage to eliminate undesired sulphur compounds which are susceptible of elimination by addition of chlorine, comprising subjecting the sewage to electrical test to determine the electrode potential .thereof, with respect to a standard reference half-cell, supplying chlorine to the sewage'at a point ahead of said electrical test, and adjusting the supply of said chlorine to maintain the detected electrode potential of the sewage substantially within a predetermined zone of electrode potential which is less than the electrode potential of chlorinetreated sewage containing free chlorine but which is indicative of the absence of the aforesaid undesired compounds.

4. A process of treating sewage, which process comprises adding a halogen to the sewage to remove undesired characteristics thereof, detecting the electrode potential of the sewage as against a standard potential, and varying the supply of halogen when and as needed'and in such quantity that the sewage will be held to a predetermined potential below'that obtainable if. free chlorine were. present, and within the range minus 150 millivolts and plus 400 millivolts when caused to impinge upon an electrode and the .lat-

ter is compared toa normal hydrogen electrode.

\ potential and translating the detected potential 1 reference potential, supplying ahalogen. to the liquid material wheniand as needed, and controlling the supply of the halogen to, the liquid material to maintain the detected difference of potential below that obtainable if free chlorine were present and above that produced when the undesired sulphide compound is present in obj ectionable amount.

6. A method of treating aqueous liquid to remove undesirable sulphur compounds susceptible of elimination by addition of a halogen, comprising detecting the electrode potential of the liquid by introducing it to .an electrode and comparing the potential of the latter to a standard reference half-cell, supplying a halogen to the liquid at a point inits flow ahead of the detection of electrode potential, whereby effects of the halogen to vary the said potential may be ascertained, and adjusting the supply of the halogen, when and as needed, to maintain the detected electrode potential within a predetermined optimum zone, which zone lies within a range corresponding to a ran'ge'of minus 150 to plus 400 millivolts which would be determined by comparing a noble metal electrode in the aqueous liquid to a standard calomel electrode corrected for equivalence to the normal hydrogen electrode, and

which zone lies substantially below the electrode potential which would be produced by addition of sufilcient halogen to afford detection of the halogen, in the treated liquid, by ordinarymethods of chemical analysis.

7. The method of removing undesired sulphide,

"compound from liquid material which method comprises, in combination, detecting the difference between the electrode potential of the liquid material and a standard reference potential, adding halogen to the liquid material to remove the undesired sulphide compound,- and suppressing the supply of halogen before the detected dif- 'ference of potential reaches that obtainable when free halogen is present in the liquid material.

8. The method of treating aqueous material to eliminate undesired characteristics thereof susceptibl of elimination by addition of a halogen in amount insufficient to leave free halogen in the material, which method comprises in combination, detecting the electrode potential of v the treated material'with respect to a standard reference potential,' and adding a halogen to the material when and as required to maintain the detected potential of the treated material below the minimum potential which would be detected if free chlorine were present in thematerial but above the maximum potential detected in the material when the undesired characteristic is present.

9. The method of testing aqueous material to determine undesired characteristics thereof susceptlble of elimination by addition of a halogen in amount lnsuflicient to leave free halogen in "the material, which method comprises in combination, treating the material with a halogen to reduce said characteristics, detecting the electrode potential of the material undergoing treat:

ment with respect to a standard reference potential and translating the detected potential 1 into an indication when said electrode potential 5. .The method of removing undesired sulphide compounds from liquid material which method comprises, in combination, detecting an electrode potential of the liquid material with respect to a departs from a value below the minimum electrode potential which would be detected if free chlorine were presentin thematerial but above the maximum electrode potential detectable in the material when the undesired characteristic is-present. r

RICHARD POMEROY. 

